STERILIZATION. 



53 



consists in the fact that the steam which escapes from the ster- 

 ihzing chamber condenses beneath the outer cover or hood 

 and falls back upon the pan over the chamber in which 

 the steam is generated. The bottom of this pan is perforated 

 with three small holes, which allow the water of condensation to 

 return into the chamber where the steam is generated. The 

 sterilizer, therefore, to a certain extent, suppHes itself with 



Fig. 13. — Steam Sterilizer, Massachusetts Board of Health. 



water, although not by any means perfectly. It is, however, less 

 likely to boil dry than other forms of sterilizers, and it has the 

 advantage of being reasonably cheap and quite efifective. The 

 space enclosed by the hood also serves as a steam-jacket and 

 helps to overcome fluctuations in temperature. A great im- 

 provement upon the ordinary Arnold sterilizer is the modifica- 

 tion of it devised by the Massachusetts Board of Health. 

 In the use of this, or any form of steam steriHzer, the time is 



